Semiconductor testing circuit and semiconductor testing method

ABSTRACT

A semiconductor testing circuit of the present invention includes a signal line which is connected to a terminal not to be tested and a plurality of terminals to be tested of a semiconductor device; switch circuits for controlling electrical connection/disconnection between the signal line and the terminals to be tested; and a resistor connected to one end of the signal line. With this configuration, in a test on the AC characteristics of an input signal, a test signal generated by an LSI tester can be inputted to the terminals to be tested through the terminal not to be tested and the signal line by turning on the switch circuits.

FIELD OF THE INVENTION

The present invention relates to a semiconductor testing circuitcontributing to a test on the AC characteristics of a semiconductordevice such as an LSI, and a semiconductor testing method.

BACKGROUND OF THE INVENTION

In a test on the AC characteristics of a semiconductor device,measurements of a propagation delay time, a setup time, a hold time, aresponse time and so on are made on an input signal and an output signalof the semiconductor device. Generally, in the test configuration, thepower supply unit and the measuring unit of an LSI tester arerespectively connected to a power supply terminal and a terminal to betested of the semiconductor device.

A method of testing the AC characteristics of a semiconductor devicewill be simply described below. As an example, the following willdescribe a test on the AC timing characteristics of a logic LSI and soon. When the AC timing characteristics of an input signal are tested,first, a test signal is inputted to a terminal to be tested (an inputterminal or an input/output terminal) and a clock signal having a givenphase difference beforehand from the test signal is inputted to a clockterminal. Next, a signal latched by a first stage flip-flop connected tothe terminal to be tested is compared with an expected value. Afterthat, the delay time and the phase difference of the input signalrelative to a reference signal are measured based on the comparisonresult. On the other hand, when the AC timing characteristics of anoutput signal are tested, the internal circuit of the semiconductordevice is operated to transmit the output signal from a terminal to betested (an output terminal or an input/output terminal) to the outsideof the semiconductor device. After that, the delay time and the phasedifference of the output signal relative to the reference signal aremeasured by comparing the output signal having been transmitted to theoutside with the expected value at a desired time.

Moreover, in tests on the AC characteristics of semiconductor devices, aplurality of semiconductor devices have been simultaneously tested inorder to suppress the cost of the tests. In other words, the powersupply unit and the measuring unit of an LSI tester are respectivelyconnected to the power supply terminal and a terminal to be tested ofeach semiconductor device, and power and signals are supplied to thesemiconductor devices at the same timing, so that the plurality ofsemiconductor devices are simultaneously tested.

However, in recent years, semiconductor devices have had a larger numberof pins and the number of measuring units has been more frequentlydeficient in simultaneous tests on a plurality of semiconductor devices.This is because in tests on AC characteristics in the prior art, thenumber of measuring units has to be at least as many as the total numberof terminals to be tested of a plurality of semiconductor devices to besimultaneously tested.

Further, in a proposed method, a path connecting one terminal toterminals to be tested is provided in a semiconductor device, so thatthe AC characteristics of a large number of terminals to be tested canbe tested using a small number of terminals (for example, see JapanesePatent Laid-Open No. 10-288647).

This method can suppress the number of terminals of semiconductordevices connected to the measuring units of an LSI tester. Thus it ispossible to test the AC characteristics of semiconductor devices with asmall number of measuring units and increase the number of semiconductordevices which can be simultaneously tested.

However, only with the path connecting one terminal to terminals to betested in a semiconductor device, the terminals to be tested have to betested one by one, so that the test time increases and the testefficiency does not improve.

DISCLOSURE OF THE INVENTION

The present invention is devised in view of the foregoing problem. Anobject of the present invention is to provide a semiconductor testingcircuit and a semiconductor testing method which can simultaneously testa large number of terminals to be tested of a semiconductor device witha small number of measuring units and improve test efficiency in a teston the AC characteristics of the semiconductor device.

In order to attain the object, a first semiconductor testing circuit ofthe present invention includes: a first signal line connected to aterminal not to be tested and a plurality of terminals to be tested ofthe semiconductor device; first switch circuits for controllingelectrical connection/disconnection between the terminals to be testedand the first signal line; and a first resistor connected to one end ofthe first signal line, wherein at least the first signal line and thefirst switch circuits are formed on the semiconductor device.

The first semiconductor testing circuit may further include a secondswitch circuit for controlling electrical connection/disconnectionbetween the first signal line and the first resistor.

Moreover, the first resistor may be provided outside the semiconductordevice.

The first semiconductor testing circuit may further include a thirdswitch circuit for controlling electrical connection/disconnectionbetween the first signal line and the terminal not to be tested.

The first semiconductor testing circuit may further include inputcondition setting circuits respectively disposed between the terminalsto be tested and the first signal line, the input condition settingcircuit being capable of changing one of the logical value and a delayamount of a signal inputted from the first signal line to the terminalto be tested through the first switch circuit. Moreover, in this case,the first switch circuit may be changed among a state in which the firstsignal line and the terminal to be tested are electrically connected toeach other via the input condition setting circuit, a state in which thefirst signal line and the terminal to be tested are electricallyconnected to each other not via the input condition setting circuit, anda state in which the first signal line and the terminal to be tested areelectrically disconnected from each other.

A second semiconductor testing circuit of the present inventionincludes: a second signal line connected to a reference terminal of thesemiconductor device, the reference terminal supplying, to the outsideof the semiconductor device, a clock signal having passed through aninternal clock tree of the semiconductor device; flip-flop circuits withselectors each of which include a flip-flop having at least an outputpin, a clock pin, and a first input pin, and a selector having secondand third input pins and electrically connecting the first input pin andone of the second and third input pins, the second input pins beingrespectively connected to terminals to be tested of the semiconductordevice, the clock pins being connected to the second signal line; fourthswitch circuits for controlling electrical connection/disconnectionbetween the second input pins of the flip-flop circuits with theselectors and the terminals to be tested; third signal lines each ofwhich connect the third input pin of the flip-flop circuits with theselectors to the output pin of the adjacent flip-flop circuit with theselector, and connect the output pin of the flip-flop circuit with theselector to a terminal not to be tested of the semiconductor device whenthe output pin is not connected to the third input pin; a fifth switchcircuit for controlling electrical connection/disconnection between thesecond signal line and the reference terminal; and a second resistorconnected to one end of the second signal line, wherein at least thesecond signal line, the flip-flop circuits with the selectors, thefourth switch circuits, the third signal lines, and the fifth switchcircuit are formed on the semiconductor device.

Further, the second resistor may be provided outside the semiconductordevice.

The second semiconductor testing circuit may further include a sixthswitch circuit for controlling electrical connection/disconnectionbetween the terminal not to be tested and the output pin of theflip-flop circuit with the selector.

A first semiconductor testing method of the present invention is asemiconductor testing method of testing, by using the firstsemiconductor testing circuit, the AC characteristics of an input signalinputted to terminals to be tested of a semiconductor device, the methodincluding the steps of: operating the first switch circuits so as toelectrically connect the terminals to be tested and the first signalline; inputting a test signal to the first signal line through theterminal not to be tested of the semiconductor device, supplying, to thesemiconductor device, a clock signal having a desired phase differencefrom the test signal, and causing first stage flip-flops provided in theinternal circuit of the semiconductor device to respectively latchsignals from the terminals to be tested; and comparing the signalslatched by the first stage flip-flops with an expected value.

In the first semiconductor testing method, when the input conditionsetting circuits are provided, the logical value or the delay amount ofeach of the input condition setting circuits is set before the testsignal is inputted to the first signal line.

A second semiconductor testing method of the present invention is asemiconductor testing method of testing, by using the secondsemiconductor testing circuit, the AC characteristics of an outputsignal supplied from terminals to be tested of the semiconductor deviceto the outside of the semiconductor device, the method including thesteps of: measuring the delay amount of the clock signal supplied fromthe reference terminal of the semiconductor device to the outside of thesemiconductor device through the internal clock tree of thesemiconductor device, the reference terminal being connected to thesecond signal line; operating the fourth switch circuits so as toelectrically connect the terminals to be tested and the second inputpins of the flip-flop circuits with the selectors, operating the fifthswitch circuit so as to electrically connect the second signal line andthe reference terminal, and operating the selectors of the flip-flopcircuits with the selectors so as to electrically connect the firstinput pins and the second input pins of the flip-flop circuits with theselectors; supplying a clock signal to the semiconductor device tooperate the internal circuit of the semiconductor device, inputting aclock signal to the reference terminal at a desired time based on themeasured delay amount when signals are supplied from last stageflip-flops provided in the internal circuit to the terminals to betested, and causing the flip-flops of the flip-flop circuits with theselectors to latch signals supplied from the terminals to be tested tothe outside of the semiconductor device; operating the selectors of theflip-flop circuits with the selectors so as to electrically connect thefirst input pins and the third input pins of the flip-flop circuits withthe selectors, and serially transmitting, to the terminal not to betested of the semiconductor device, the signals latched by the flip-flopcircuits with the selectors; and comparing the signals seriallytransmitted to the terminal not to be tested with an expected value.

According to a preferred embodiment of the present invention, in a teston the AC characteristics of a semiconductor device, it is possible tosimultaneously test a large number of terminals of the semiconductordevice with a small number of measuring units, thereby improving testefficiency. Further, it is possible to increase the number ofsemiconductor devices which can be simultaneously tested, therebyreducing the cost of equipment and test.

In other words, since the resistor (termination resistor) is provided onone end of the first signal line, it is possible to suppress thereflection of a signal on the first signal line. Therefore, in a test onthe AC characteristics of the input signal inputted to the terminals tobe tested, the test signal can be inputted simultaneously to theterminals to be tested through the first signal line, so that a largenumber of terminals of, the semiconductor device can be simultaneouslytested with a small number of measuring units.

Moreover, by providing the input condition setting circuits, signalshaving different logical values and delay amounts can be simultaneouslyinputted to the respective terminals to be tested. Therefore, it ispossible to test the terminals to be tested under different conditions,thereby increasing the number of terminals which can be simultaneouslytested.

Further, by providing the flip-flop circuits with the selectors, in atest on the AC characteristics of the output signals supplied from theterminals to be tested to the outside of the semiconductor device, theoutput signals can be latched by the flip-flop circuits with theselectors and the latched signals can be serially transmitted to thesingle terminal not to be tested, the terminal being connected to an LSItester. Thus it is possible to simultaneously test a large number ofterminals of the semiconductor device with a small number of measuringunits.

As described above, according to the semiconductor testing circuit andthe semiconductor testing method of the present invention, it ispossible to simultaneously test a large number of terminals of thesemiconductor device with a small number of resources. Thus it ispossible to improve the test efficiency of the semiconductor device andreduce the cost of test and equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example of the testconfiguration of a semiconductor device including a semiconductortesting circuit according to a first embodiment of the presentinvention;

FIG. 2 is a flowchart showing an example of a semiconductor testingmethod according to the first embodiment of the present invention;

FIG. 3 is a schematic diagram showing an example of the testconfiguration of a semiconductor device including a first modificationof the semiconductor testing circuit according to the first embodimentof the present invention;

FIG. 4 is a schematic diagram showing an example of the testconfiguration of a semiconductor device including a second modificationof the semiconductor testing circuit according to the first embodimentof the present invention;

FIG. 5 is a schematic diagram showing an example of the testconfiguration of a semiconductor device including a third modificationof the semiconductor testing circuit according to the first embodimentof the present invention;

FIG. 6 is a schematic diagram showing an example of the testconfiguration of a semiconductor device including a semiconductortesting circuit according to a second embodiment of the presentinvention;

FIG. 7 shows a structural example of an input condition setting circuitincluded in the semiconductor testing circuit according to the secondembodiment of the present invention;

FIG. 8 shows a structural example of the input condition setting circuitincluded in the semiconductor testing circuit according to the secondembodiment of the present invention;

FIG. 9 is a flowchart showing an example of a semiconductor testingmethod according to the second embodiment of the present invention;

FIG. 10 is a schematic diagram showing an example of the testconfiguration of a semiconductor device including a semiconductortesting circuit according to a third embodiment of the presentinvention; and

FIG. 11 is a flowchart showing an example of a semiconductor testingmethod according to the third embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

FIG. 1 schematically shows the test configuration of a semiconductordevice including a semiconductor testing circuit according to a firstembodiment of the present invention. The semiconductor testing circuitof the first embodiment is used for testing the AC characteristics of aninput signal and an output signal of a semiconductor device such as anLSI. The configurations of an LSI tester and the semiconductor deviceare partially shown in FIG. 1.

The first embodiment will describe an example of a test on the AC timingcharacteristics of a semiconductor device including first stageflip-flops and last stage flip-flops which are respectively connected toa plurality of input/output terminals. As a matter of course, the use ofthe semiconductor testing circuit and the semiconductor testing methodof the present invention is not limited to the semiconductor deviceconfigured thus.

As shown in FIG. 1, a semiconductor testing circuit 100 is provided in asemiconductor device 200 that is a device to be measured. Thesemiconductor device 200 is mounted on a load board 400 acting as aninterface connecting the semiconductor device 200 and an LSI tester 300during a test. The semiconductor device 200 may be mounted on a wafer ormolded in a package. The LSI tester 300, the semiconductor device 200,and the semiconductor testing circuit 100 will be described in thisorder.

In the LSI tester 300, a power supply unit 301 generates power suppliedto the semiconductor device 200. The power supply unit 301 is connected,via the load board 400, to a pad 202 of a power supply terminal 201provided in the semiconductor device 200.

Further, a first measuring unit 302 has a function of generating, at anygiven time, a test signal (logic signal) to be supplied to thesemiconductor device 200, and a function of observing an output signal(logic signal) from the semiconductor device 200. The first measuringunit 302 is connected, via the load board 400, to a pad 204 of a firstinput/output terminal 203 provided in the semiconductor device 200.

To be specific, the first measuring unit 302 includes a driver 303 forgenerating the test signal at the given time based on a reference signalgenerated in the LSI tester 300, and a comparator 304 for observing thelogical value of the output signal by comparing the output signal fromthe semiconductor device 200 with a specified value. The LSI tester 300measures the delay time of the output signal relative to the referencesignal and a phase difference and so on between the output signal andthe reference signal by comparing an observation result of thecomparator 304 (the logical value of the output signal) and an expectedvalue at a desired time.

A second measuring unit 305 has a function of generating, at any giventime, a clock signal to be supplied to the semiconductor device 200, anda function of observing the clock signal from the semiconductor device200, that is, the clock signal having passed through the internal clocktree of the semiconductor device 200 (hereinafter, sometimes referred toas an output clock signal). The second measuring unit 305 is connected,via the load board 400, to a pad 210 of a clock terminal 209 provided inthe semiconductor device 200.

To be specific, the second measuring unit 305 includes a driver 306 forgenerating the clock signal at the given time based on the referencesignal generated in the LSI tester 300, and a comparator 307 forobserving the rising edge and the falling edge of the output clocksignal by comparing the output clock signal and a specified value. TheLSI tester 300 measures the delay time of the output clock signalrelative to the reference signal and a phase difference and so onbetween the output clock signal and the reference signal by observingthe timing of the rising edge and the falling edge of the output clocksignal based on an observation result of the comparator 307.

The following will describe the semiconductor device 200. Thesemiconductor device 200 includes, as external terminals, the powersupply terminal 201 connected to the power supply unit 301 of the LSItester 300, the first input/output terminal 203 connected to the firstmeasuring unit 302 of the LSI tester 300, second input/output terminals205 which are terminals to be tested, and the clock terminal (referenceterminal) 209 connected to the second measuring unit 305 of the LSItester 300. These terminals include at least pads for connection to anexternal circuit. Further, in this configuration, the secondinput/output terminals 205 and the clock terminal 209 include inputbuffers (gates) 207 and 211 and output buffers (tri-state buffers) 208and 212. These buffers are connected to pads 206 of the secondinput/output terminals 205 and the pad 210 of the clock terminal 209.

The pads 206 of the second input/output terminals 205 are connected tothe data input pins of first stage flip-flops 213 via the input buffers207. Further, the pads 206 of the second input/output terminals 205 areconnected to the data output pins of last stage flip-flops 214 via theoutput buffers 208.

The pad 210 of the clock terminal 209 is connected to an internal clocktree 215 of the semiconductor device 200 via the input buffer 211 andthe output buffer 212. The clock terminal 209 is a terminal which isfed, from the outside, with the clock signal for operating the internalcircuit of the semiconductor device 200 and supplies, to the outside,the clock signal (output clock signal) having passed through theinternal clock tree 215 of the semiconductor device 200. The clock pinsof the first stage flip-flops 213 and the last stage flip-flops 214 areconnected to the internal clock tree 215.

The following will describe a test on a single semiconductor device. Asa matter of course, a plurality of semiconductor devices can besimultaneously tested. In this case, the power supply unit 301 and themeasuring units 302 and 305 are connected to each of the semiconductordevices.

Further, the following explanation will describe an example in which theterminal fed with the clock signal from the outside and the terminal forsupplying the clock signal to the outside are included in the singleclock terminal 209. As a matter of course, these terminals may beseparately provided.

The following will describe the semiconductor testing circuit 100. Inthe semiconductor testing circuit 100, a signal line (first signal line)101 is made up of a main part and branch parts. One end of the main partof the signal line 101 is connected near the pad 204 of the firstinput/output terminal (not to be tested) 203 connected to the firstmeasuring unit 302 of the LSI tester 300. The branch parts of the signalline 101 are respectively provided for the second input/output terminals205. Each of the branch parts is connected near the pad 206 of thesecond input/output terminal 205 via a switch circuit (first switchcircuit) 102. Each of the switch circuits 102 controls electricalconnection/disconnection between the second input/output terminal 205and the signal line 101. The other end of the main part of the signalline 101 is connected to a resistor (first resistor) 103 acting as atermination resistor. The signal line 101, the switch circuits 102, andthe resistor 103 are formed on the semiconductor device 200.

With this configuration, during a test on the AC timing characteristicsof the input signal, the switch circuits 102 connected to the secondinput/output terminals 205 to be tested are turned on, so that a testsignal supplied from the LSI tester 300 to the first input/outputterminal 203 can be inputted, through the path of the signal line 101,to the gates (input buffers 207) of the second input/output terminals205 to be tested.

Further, during a test on the AC timing characteristics of the outputsignal, the switch circuits 102 connected to the second input/outputterminals 205 to be tested are turned on, so that output signals fromthe output buffers 208 of the second input/output terminals 205 can betransmitted to the LSI tester 300 through the signal line 101 and thefirst input/output terminal 203.

During a normal operation of the semiconductor device 200, the switchcircuits 102 are turned off, so that the second input/output terminals205 can be disconnected from the signal line 101. Thus during the normaloperation of the semiconductor device 200, the semiconductor testingcircuit 100 does not affect the operation of the internal circuit of thesemiconductor device 200.

Further, only necessary ones of the multiple terminals to be tested canbe electrically connected to the signal line 101, and the otherterminals not to be simultaneously fed with the test signal can bedisconnected from the signal line 101. Moreover, during a test on the ACtiming characteristics of the output signal, any one of the multipleterminals to be tested can be electrically connected to the signal line101.

The switch circuit 102 can be turned on/off by providing a circuit (notshown) in, for example, the semiconductor device 200 to turn on/off theswitch circuit 102 according to an instruction signal optionallygenerated in the LSI tester 300.

The resistor 103 provided on the end of the signal line 101 is disposednear the second input/output terminal 205 farthest from the junctionpoint of the first input/output terminal 203 and the signal line 101.The resistor 103 can suppress the reflection of a signal transmittedthrough the signal line 101 even when the signal is a pulse signal suchas a logic signal or an AC sine wave signal.

In the test on the AC timing characteristics, the delay time of a signaltransmitted between the pad of a terminal to be tested and the firststage or last stage flip-flop is observed. Thus the signal line 101 isconnected as close as possible to the pads of the terminals to betested. Further, in order to transmit a signal having an undistortedwaveform through the signal line 101, the lengths of the branch parts ofthe signal line 101 are minimized. Therefore, it is preferable to formthe semiconductor testing circuit 100 in a region under a region wherethe pads of the terminals to be tested are formed.

The following will describe a method of testing the AC timingcharacteristics, as a semiconductor testing method according to thefirst embodiment of the present invention. In a test on the AC timingcharacteristics of the input signal, the test signal is supplied to theterminals to be tested in the semiconductor device 200 and the clocksignal is supplied to the clock terminal 209 of the semiconductor device200 at a desired time. Then, by comparing a signal latched by the firststage flip-flop 213 with the expected value, the delay time of the inputsignal relative to the reference signal and a phase difference and so onbetween the input signal and the reference signal are measured. In atest on the AC timing characteristics of the output signal, the internalcircuit of the semiconductor device 200 is operated to measure the delaytime and the phase difference of the output signal relative to thereference signal by comparing the output signal from the semiconductordevice 200 with the expected value at a desired time.

Referring to FIG. 2, the following will specifically describe an exampleof a test on the AC timing characteristics of the input signal.

First, the LSI tester 300 starts power supply (power-up) to thesemiconductor device 200 that is a device to be measured, and thenapplies a reset signal to the semiconductor device 200 (step S201).Thereafter, the LSI tester 300 switches the semiconductor device 200 toa state (test mode) in which the AC timing characteristics of the inputsignal are tested (step S202).

Next, the LSI tester 300 turns on the switch circuits 102 connected tothe second input/output terminals 205 to be simultaneously tested andelectrically connects the second input/output terminals to the signalline 101 (step S203).

Then, the LSI tester 300 generates, in the first measuring unit 302, thetest signal for testing the AC timing characteristics of the inputsignal, inputs the test signal to the signal line 101 through the firstinput/output terminal 203, generates the clock signal in the secondmeasuring unit 305 at a desired time, and inputs the clock signal to theinternal clock tree 215 through the clock terminal 209 (step S204). Adesired phase difference is set between the clock signal and the testsignal. The set value of the phase difference is an AC timingcharacteristic value to be tested and corresponds to, for example, asetup time and a hold time.

The test signal generated in the first measuring unit 302 is inputtedthrough the signal line 101 to the input buffers (gates) 207 of thesecond input/output terminals 205 to be simultaneously tested. The testsignal having been inputted to the input buffers 207 is inputted to thedata input pins of the first stage flip-flops 213. On the other hand,the clock signal generated in the second measuring unit 305 is inputtedto the clock pins of the first stage flip-flops 213 through a part ofthe internal clock tree 215.

The first stage flip-flop 213 latches the signal inputted to the datainput pin, at the rising edge or the falling edge of the clock signal(step S205). The signal latched by the first stage flip-flop 213 iscompared with the expected value in a comparator circuit (not shown)provided beforehand in the semiconductor device 200 (step S206). Theexpected value is the logical value of the test signal. Based on thecomparison result, it is possible to measure the delay time and so on ofthe input signal relative to the reference signal. The signal latched bythe first stage flip-flop 213 may be transmitted from an externalterminal (not shown) of the semiconductor device 200 to the LSI tester300 and may be compared with the expected value in the LSI tester 300.

The following will describe an example of a test on the AC timingcharacteristics of the output signal.

First, the LSI tester 300 starts power supply to the semiconductordevice 200, and then applies the reset signal to the semiconductordevice 200. Thereafter, the LSI tester 300 switches the semiconductordevice 200 to a state (test mode) in which the AC timing characteristicsof the output signal are tested.

Next, the LSI tester 300 turns on the switch circuits 102 connected tothe second input/output terminals 205 to be simultaneously fed with thetest signal, and electrically connects the second input/output terminals205 to the signal line 101.

Then, the LSI tester 300 generates, in the first measuring unit 302, thetest signal for testing the AC timing characteristics of the outputsignal, inputs the test signal to the signal line 101 through the firstinput/output terminal 203, generates, in the second measuring unit 305,the clock signal for operating the internal circuit of the semiconductordevice 200, and inputs the clock signal to the internal clock tree 215through the clock terminal 209.

The test signal generated in the first measuring unit 302 is inputtedthrough the signal line 101 to the input buffers (gates) 207 of thesecond input/output terminals 205 connected to the switch circuits 102which have been turned on. The test signal inputted to the input buffers207 is inputted to the internal circuit of the semiconductor device 200.

The internal circuit of the semiconductor device 200 is operated inresponse to the test signal and the clock signal. Consequently, when theoutput signal is transmitted only from one of the last stage flip-flops214, the LSI tester 300 turns on the switch circuit 102 connected to thesecond input/output terminal 205 fed with the output signal from thelast stage flip-flop 214 and electrically connects the firstinput/output terminal 203 and the second input/output terminal 205connected to the switch circuit 102 which has been turned on. On theother hand, when the output signals are transmitted from the pluralityof last stage flip-flops 214, the LSI tester 300 turns on the switchcircuit 102 connected to any one of the second input/output terminals205 connected to the last stage flip-flops 214, and electricallyconnects the first input/output terminal 203 and the second input/outputterminal 205 connected to the switch circuit 102 which has been turnedon.

One of the switch circuits is turned on thus, so that the output signalsupplied to the outside of the semiconductor device 200 from the secondinput/output terminal 205 connected to the switch circuit having beenturned on is transmitted to the first measuring unit 302 of the LSItester 300.

The first measuring unit 302 observes the output signal. The LSI tester300 compares the logical value of the output signal having been observedin the first measuring unit 302 with the expected value (the logicalvalue of the test signal) at a desired time, and measures the delay timeand so on of the output signal relative to the reference signal based onthe comparison result. In this case, a phase difference between thedesired time and the rising edge or the falling edge of the referencesignal is an AC timing characteristic value to be tested. For example,the AC timing characteristic value corresponds to a setup time and ahold time.

In the first embodiment, when the AC timing characteristics of theoutput signal are tested, the test signal generated in the LSI tester isinputted to the internal circuit of the semiconductor device 200 throughthe external terminal of the semiconductor device 200. The test signalmay be generated by a test signal generating circuit provided beforehandin the semiconductor device 200.

Further, in the first embodiment, the input signal and the output signalof the semiconductor device are logical signals, that is, thesemiconductor device is a logic LSI and the like. As a matter of course,the present invention can be similarly implemented even when the inputsignal and the output signal are pulse signals other than a logicalsignal. Moreover, the present invention can be similarly implemented inan analog-digital mixed LSI and so on. In the case of an analog-digitalmixed LSI, an LSI tester generates, for example, an AC sine wave signalas a test signal at any given time. Further, the LSI tester compares thevoltage of an AC signal (output signal) from the semiconductor devicewith a specified value and observes the voltage. Moreover, based on theobservation result, the LSI tester measures the delay time and so on ofthe AC signal from the semiconductor device relative to a referencesignal.

As described above, the semiconductor testing circuit 100 is provided inthe semiconductor device 200 that is a device to be measured. Thus it ispossible to test the AC characteristics of the semiconductor device 200with a small number of terminals of the semiconductor device 200.Particularly, in a test on the AC characteristics of the input signal, alarge number of terminals can be simultaneously tested.

The following will describe modifications of the first embodiment. Thesemiconductor testing methods of the following modifications are similarto the semiconductor testing method using the semiconductor testingcircuit of FIG. 1 and thus the explanation thereof is omitted.

FIG. 3 schematically shows the test configuration of a semiconductordevice including a first modification of the semiconductor testingcircuit according to the first embodiment of the present invention.Members corresponding to the members illustrated in FIG. 1 are indicatedby the same reference numerals and the explanation thereof is omitted.

As shown in FIG. 3, the first modification of the semiconductor testingcircuit is different from the semiconductor testing circuit of FIG. 1 inthat a switch circuit (second switch circuit) 104 for controllingelectrical connection/disconnection between one end of a signal line 101and a resistor 103 is provided between the end of the signal line 101and the resistor 103.

With this configuration, when AC characteristics are tested, the switchcircuit 104 is turned on to electrically connect the signal line 101 andthe resistor 103, thereby suppressing the reflection of a pulse signalsuch as a logical signal or an AC signal. Further, when DCcharacteristics are tested, the switch circuit 104 is turned off todisconnect the signal line 101 from the resistor 103, so that the DCcharacteristics can be tested without considering a current or voltagedivided by the resistor 103.

The switch circuit 104 can be turned on/off by providing a circuit in,for example, a semiconductor device 200 to turn on/off the switchcircuit 104 according to an instruction signal optionally generated inthe LSI tester 300.

The following will describe a second modification of the semiconductortesting circuit according to the first embodiment of the presentinvention. FIG. 4 schematically shows the test configuration of asemiconductor device including the second modification of thesemiconductor testing circuit according to the first embodiment of thepresent invention. Members corresponding to the members illustrated inFIG. 1 are indicated by the same reference numerals and the explanationthereof is omitted.

As shown in FIG. 4, the second modification of the semiconductor testingcircuit is different from the semiconductor testing circuit of FIG. 1 inthat a resistor 401 connected to one end of a signal line 101 isprovided outside a semiconductor device 200, that is, on a load board400. To be specific, the end of the signal line 101 is connected to apad 217 of an external terminal 216 of the semiconductor device 200which is connected via the load board 400 to the resistor 401 providedon the load board 400.

With this configuration, it is not necessary to form, on thesemiconductor device 200, the resistor connected to the end of thesignal line 101. Thus it is possible to suppress the unevencharacteristics of termination resistors between semiconductor devicesand reduce the circuit area of the semiconductor device.

When the external terminal 216 is a terminal only for a test, as shownin FIG. 4, the signal line 101 may be directly connected to the externalterminal 216. When the external terminal 216 is a terminal for actualuse, the signal line 101 may be disconnected from the external terminal216 during actual use by providing a switch circuit for controllingelectrical connection/disconnection between the signal line 101 and theexternal terminal 216.

The following will describe a third modification of the semiconductortesting circuit according to the first embodiment of the presentinvention. FIG. 5 schematically shows the test configuration of asemiconductor device including the third modification of thesemiconductor testing circuit according to the first embodiment of thepresent invention. Members corresponding to the members illustrated inFIG. 1 are indicated by the same reference numerals and the explanationthereof is omitted.

As shown in FIG. 5, the third modification of the semiconductor testingcircuit is different from the semiconductor testing circuit of FIG. 1 inthat a switch circuit (third switch circuit) 105 is provided forcontrolling electrical connection/disconnection between a firstinput/output terminal 203, which is connected to an LSI tester 300, anda signal line 101.

With this configuration, when AC characteristics are tested, the signalline 101 and the first input/output terminal 203 can be electricallyconnected to each other by turning on the switch circuit 105, and thesignal line 101 can be disconnected from the first input/output terminal203 during actual use. Therefore, the first input/output terminal 203connected to the signal line 101 does not have to be a terminal only fora test and can be an external terminal applicable to actual use.

The switch circuit 105 can be turned on/off by providing a circuit in,for example, a semiconductor device 200 to turn on/off the switchcircuit 105 according to an instruction signal optionally generated inthe LSI tester 300.

As described above, according to the first embodiment, in a test on theAC characteristics of the input signal, the test signal can besimultaneously inputted from the single input/output terminal to theplurality of input/output terminals and a large number of terminals canbe simultaneously tested using a small number of terminals. In the firstembodiment, the terminals to be tested are input/output terminals. Aninput terminal and an output terminal can be similarly tested.

Second Embodiment

FIG. 6 schematically shows the test configuration of a semiconductordevice including a semiconductor testing circuit according to a secondembodiment of the present invention. Members corresponding to themembers illustrated in the first embodiment are indicated by the samereference numerals and the explanation thereof is omitted. Theconfigurations of an LSI tester and the semiconductor device arepartially shown in FIG. 6.

The semiconductor testing circuit of the second embodiment is used fortesting the AC characteristics of an input signal of the semiconductordevice such as an LSI. The second embodiment will describe an example ofa test on the AC timing characteristics of the input signal of thesemiconductor device in which first stage flip-flops and last stageflip-flops are respectively connected to a plurality of input/outputterminals. As a matter of course, the use of the semiconductor testingcircuit and the semiconductor testing method of the present invention isnot limited to the semiconductor device configured thus. The followingwill describe a test on a single semiconductor device. As a matter ofcourse, a plurality of semiconductor devices can be simultaneouslytested.

As shown in FIG. 6, a semiconductor testing circuit 110 is differentfrom the semiconductor testing circuit 100 illustrated in the firstembodiment in that input condition setting circuits 111 are providedbetween terminals to be tested (second input/output terminals 205) and asignal line (first signal line) 101. The input condition setting circuit111 can change the input conditions (logical value and delay amount) ofeach signal inputted from the signal line 101 to each terminal to betested through a switch circuit (first switch circuit) 102.

In the first embodiment, the same test signals are simultaneouslyinputted to terminals to be tested during a test on the AC timingcharacteristics of the input signal, whereas in the second embodiment,with the input condition setting circuits 111, the logical values oftest signals simultaneously inputted to terminals to be tested can berespectively set for the terminals to be tested. Further, in the firstembodiment, during a test on the AC timing characteristics of the inputsignal, the test signals are inputted at the same input timing toterminals to be tested, whereas in the second embodiment, the inputcondition setting circuits 111 can set input timing (delay amount)respectively for terminals to be tested.

For example, the input condition setting circuit 111 can be made up of alogical circuit including a buffer 112, an inverter 113, and a selector114 as shown in FIG. 7, or made up of a delay circuit including aplurality of delay elements 115 connected in series as shown in FIG. 8.Moreover, the input condition setting circuit 111 may be a combinedcircuit (not shown) of the logical circuit of FIG. 7 and the delaycircuit of FIG. 8. The logical value and the delay amount of the inputcondition setting circuit 111 can be set by providing a circuit in, forexample, a semiconductor device 200 to set the logical value and thedelay amount of the input condition setting circuit 111 according to aninstruction signal optionally generated in an LSI tester 300.

In a test on the AC timing characteristics of the input signal, thedelay time of a signal transmitted between the pad of the terminal to betested and the first stage flip-flop is observed. Thus the signal line101 is connected as close as possible to the pads of the terminals to betested. Further, in order to transmit a signal having an undistortedwaveform through the signal line 101, the lengths of the branch parts ofthe signal line 101 are minimized. Therefore, it is preferable to formthe semiconductor testing circuit 110 in a region under a region wherethe pads of the terminals to be tested are formed.

Referring to FIG. 9, the following will describe an example of a methodof testing the AC timing characteristics of the input signal, as asemiconductor testing method according to the second embodiment of thepresent invention.

First, the LSI tester 300 starts power supply (power-up) to asemiconductor device 200 that is a device to be measured, and thenapplies a reset signal to the semiconductor device 200 (step S901).Thereafter, the LSI tester 300 switches the semiconductor device 200 toa state (test mode) in which the AC timing characteristics of the inputsignal are tested (step S902).

Next, the LSI tester 300 sets the logical values and the delay amountsof the input condition setting circuits 111 (step S903). Thus thelogical value and the input timing (delay amount) of a test signal areset for each of the second input/output terminals 205 that are terminalsto be tested.

Next, the LSI tester 300 turns on the switch circuits 102 connected tothe second input/output terminals 205 to be simultaneously tested, andelectrically connects the second input/output terminals 205 to thesignal line 101 (step S904).

Then, the LSI tester 300 generates, in a first measuring unit 302, thetest signal for testing the AC timing characteristics of the inputsignal, inputs the test signal to the signal line 101 through a firstinput/output terminal 203, generates a clock signal in a secondmeasuring unit 305 at a desired time, and inputs the clock signal to aninternal clock tree 215 through a clock terminal 209 (step S905). Adesired phase difference is set between the clock signal and the testsignal. The set value of the phase difference is an AC timingcharacteristic value to be tested and corresponds to, for example, asetup time and a hold time. When the input timing of the test signal canbe changed by the input condition setting circuit 111, the AC timingcharacteristic value of each terminal to be tested can be set by theinput condition setting circuit 111.

The test signal generated in the first measuring unit 302 is inputtedthrough the input condition setting circuits 111 to input buffers(gates) 207 of the second input/output terminals 205 to besimultaneously tested. Therefore, the input buffers 207 of the secondinput/output terminals 205 are fed with the test signals whose logicalvalues and delay amounts have been set by the input condition settingcircuits 111. The test signals having been inputted to the input buffers207 are inputted to the data input pins of first stage flip-flops 213.

On the other hand, the clock signal generated in the second measuringunit 305 is inputted to the clock pins of the first stage flip-flops 213through a part of the internal clock tree 215.

The first stage flip-flop 213 latches the signal inputted to the datainput pin, at the rising edge or the falling edge of the clock signal(step S906). The signal latched by the first stage flip-flop 213 iscompared with an expected value in a comparator circuit (not shown)provided beforehand in the semiconductor device 200 (step S907). Theexpected value is the logical value of the test signal. Based on thecomparison result, it is possible to measure the delay time and so on ofthe input signal relative to a reference signal. The signal latched bythe first stage flip-flop 213 may be transmitted from an externalterminal (not shown) of the semiconductor device 200 to the LSI tester300 and may be compared with the expected value in the LSI tester 300.

As described above, according to the second embodiment, the inputconditions (logical value, delay amount, and so on) of terminals to betested can be set in a test on the AC characteristics of the inputsignal. Thus it is possible to simultaneously test a larger number ofterminals.

In the second embodiment, the input signal of the semiconductor deviceis a logical signal, that is, the semiconductor device is a logic LSIand the like. As a matter of course, the present invention can besimilarly implemented even when the input signal is a pulse signal otherthan a logical signal. Moreover, the present invention can be similarlyimplemented in an analog-digital mixed LSI and so on. In the case of ananalog-digital mixed LSI, the input condition setting circuit 111 maydelay the phase of an AC signal serving as a test signal.

As in the semiconductor testing circuit of the first embodiment, aswitch circuit (second switch circuit) for controlling electricalconnection/disconnection between one end of the signal line 101 and aresistor 103 may be provided between the end of the signal line 101 andthe resistor 103 (first modification), a resistor may be providedoutside the semiconductor device 200 so as to be connected to the end ofthe signal line 101 (second modification), or a switch circuit (thirdswitch circuit) may be provided for controlling electricalconnection/disconnection between the first input/output terminal 203 notto be tested and the signal line 101 (third modification).

In the second embodiment, the terminal to be tested is an input/outputterminal. An input terminal can be similarly tested.

Further, the switch circuit 102 for controlling electricalconnection/disconnection between the second input/output terminal 205 tobe tested and the signal line 101 may be changed among a state in whichthe second input/output terminal 205 is electrically connected to thesignal line 101 via the input condition setting circuit 111, a state inwhich the second input/output terminal 205 is electrically connected tothe signal line 101 not via the input condition setting circuit 111,that is, the second input/output terminal 205 is directly andelectrically connected to the signal line 101, and a state in which thesecond input/output terminal 205 is electrically disconnected from thesignal line 101. Thus as in the first embodiment, the AC timingcharacteristics of an output signal can be tested.

Third Embodiment

FIG. 10 schematically shows the test configuration of a semiconductordevice including a semiconductor testing circuit according to a thirdembodiment of the present invention. Members corresponding to themembers illustrated in the first embodiment are indicated by the samereference numerals and the explanation thereof is omitted. Theconfigurations of an LSI tester and the semiconductor device arepartially shown in FIG. 10.

The semiconductor testing circuit of the third embodiment is used fortesting the AC characteristics of an output signal of the semiconductordevice such as an LSI. The third embodiment will describe an example ofa test on the AC timing characteristics of the output signal of thesemiconductor device in which first stage flip-flops and last stageflip-flops are respectively connected to a plurality of input/outputterminals. As a matter of course, the use of the semiconductor testingcircuit and the semiconductor testing method of the present invention isnot limited to the semiconductor device configured thus. The followingwill describe a test on a single semiconductor device. As a matter ofcourse, a plurality of semiconductor devices can be simultaneouslytested.

A semiconductor testing circuit 120 is different from the semiconductortesting circuit 100 of the first embodiment in that output signalstransmitted from a plurality of last stage flip-flops 214 are capturedfrom second input/output terminals 205 connected to the last stageflip-flops 214, and are serially transferred to a first input/outputterminal 203 connected to an LSI tester 300.

The semiconductor testing circuit 120 will be specifically describedbelow. In FIG. 10, a flip-flop circuit 121 provided with a selector foreach of the second input/output terminals 205 to be tested includes aflip-flop 129 having a first input pin (data input pin), a clock pin,and an output pin (data output pin), and a selector 130 having a secondinput pin and a third input pin one of which is electrically connectedto the first input pin of the flip-flop 129.

Each of the second input pins of the selectors 130 is connected to asignal line 122. Each of the signal lines 122 is connected near a pad206 of the second input/output terminal 205 to be tested, via a switchcircuit (fourth switch circuit) 123. Each of the switch circuits 123controls electrical connection/disconnection between the second inputpin of the selector 130 and the second input/output terminal 205 to betested.

Of the flip-flop circuits 121 with the selectors, in each of theflip-flop circuits 121 other than the last stage flip-flop circuit 121with the selector near the first input/output terminal 203 that isconnected to the LSI tester 300 and is not to be tested, each of thethird input pins of the selectors 130 is connected to the output pin ofthe flip-flop 129 of the adjacent flip-flop circuit 121 with theselector via a signal line (third signal line) 124. On the other hand,the third input pin of the last stage flip-flop circuit 121 with theselector is not connected to the output pins of the other flip-flopcircuits with the selectors but is connected near a pad 204 of the firstinput/output terminal 203 via a signal line (third signal line) 125.

The clock pins of the flip-flops 129 of the flip-flop circuits 121 withthe selectors are connected to a signal line (second signal line) 126.The signal line 126 is connected to a clock terminal 209 serving as areference terminal, via a switch circuit (fifth switch circuit) 127. Theswitch circuit 127 controls electrical connection/disconnection betweenthe signal line 126 and the clock terminal 209.

To one end of the signal line 126, a resistor (second resistor) 128 isconnected as a termination resistor. The resistor 128 is disposed nearthe second input/output terminal 205 farthest from the junction point ofthe clock terminal 209 and the signal line 126. The resistor 128 cansuppress the reflection of a clock signal transmitted through the signalline 126.

The flip-flop circuits 121 with the selectors, the signal lines 122, theswitch circuits 123, the signal lines 124, the signal line 125, thesignal line 126, the switch circuit 127, and the resistor 128 are formedon a semiconductor device 200.

With this configuration, an output signal transmitted from an outputbuffer 208 of the second input/output terminal 205 can be inputted tothe flip-flop circuit 121 with the selector through the signal line 122,and the output signal can be latched by the flip-flop circuit 121 withthe selector. The flip-flop circuits 121 with the selectors areconnected in series via the signal lines 124, so that the signalslatched by the flip-flop circuits 121 with the selectors can be seriallytransmitted to the first input/output terminal 203 through the signallines 124 and 125.

One of the input pins of the selector 130 is electrically connected tothe first input pin of the flip-flop 129 and the connected pin isselected by providing a circuit (not shown) in, for example, thesemiconductor device 200 to operate the selector 130 according to aninstruction signal optionally generated in the LSI tester 300.

The switch circuits 123 and 127 are turned on/off by providing a circuit(not shown) in, for example, the semiconductor device 200 to turn on/offthe switch circuits 123 and 127 according to instruction signalsoptionally generated in the LSI tester 300.

With this configuration, when the AC timing characteristics of theoutput signal are tested, the switch circuits 123 and 127 are turned onand thus the output signals transmitted from the output buffers 208 ofthe second input/output terminals 205 to be tested can be latched by theflip-flop circuits 121 with the selectors. Further, only necessary onesof the multiple terminals to be tested can be electrically connected tothe flip-flop circuits 121 with the selectors.

During a normal operation of the semiconductor device 200, the switchcircuits 123 and 127 are turned off, so that the input/output terminals205 to be tested and the clock terminal 209 can be disconnected from thesemiconductor testing circuit 120. Thus during a normal operation of thesemiconductor device 200, the semiconductor testing circuit 120 does notaffect the operation of the internal circuit of the semiconductor device200.

In a test on the AC timing characteristics of the output signal, thedelay time of a signal transmitted between the pad of the terminal to betested and the last stage flip-flop is observed. Thus the signal lines122 are connected as close as possible to the pads of the terminals tobe tested. Further, in order to transmit a signal having an undistortedwaveform through the signal lines 122, 124, 125 and 126, the lengths ofthe signal lines 122, 124, 125 and 126 are minimized. Therefore, it ispreferable to mount the semiconductor testing circuit 120 under theterminals to be tested.

Referring to FIG. 11, the following will describe an example of a methodof testing the AC timing characteristics of the output signal, as asemiconductor testing method according to the third embodiment of thepresent invention.

First, the LSI tester 300 starts power supply (power-up) to thesemiconductor device 200, and then applies a reset voltage to thesemiconductor device 200 (step S1101). Thereafter, the LSI tester 300switches the semiconductor device 200 to a state (test mode) in whichthe AC timing characteristics of the output signal are tested (stepS1102).

Next, the LSI tester 300 operates the internal circuit of thesemiconductor device 200 to transmit a clock signal (output clocksignal) having passed through an internal clock tree 215, from the clockterminal 209 to the LSI tester 300 (step S1103). When the internalcircuit of the semiconductor device 200 is operated, the LSI tester 300generates a clock signal for operating the internal circuit of thesemiconductor device 200 and supplies the generated clock signal to thesemiconductor device 200. Moreover, a data signal for operating theinternal circuit of the semiconductor device 200 may be generated in theLSI tester 300 or in the semiconductor device 200.

Next, the LSI tester 300 observes the output clock signal from the clockterminal 209 in a second measuring unit 305 and measures the delay time(delay amount) and so on of the output clock signal relative to areference signal based on the observation result (step S1104).

Then, the LSI tester 300 turns on the switch circuits 123 toelectrically connect the second input/output terminals 205 and thesecond input pins of the selectors 130 of the flip-flop circuits 121with the selectors, turns on the switch circuit 127 to electricallyconnect the signal line 126 and the clock terminal 209 serving as areference terminal, and operates the selectors 130 of the flip-flopcircuits 121 with the selectors so as to electrically connect the firstinput pins of the flip-flops 129 and the second input pins (the secondinput/output terminals 205 to be tested) of the selectors 130 in theflip-flop circuits 121 with the selectors (step S1105).

Next, the LSI tester 300 operates the internal circuit of thesemiconductor device 200 again to transmit output signals from the laststage flip-flops 214 (step S1106). At this point, the clock terminal 209is inhibited from supplying the output clock signal to the outside ofthe semiconductor device 200. To be specific, an output buffer 212 ofthe clock terminal 209 is disabled. Further, when the internal circuitof the semiconductor device 200 is operated, the LSI tester 300generates a clock signal for operating the internal circuit of thesemiconductor device 200 and supplies the generated clock signal to thesemiconductor device 200. A data signal for operating the internalcircuit of the semiconductor device 200 may be generated in the LSItester 300 or in the semiconductor device 200.

Next, when the output signals are transmitted from the last stageflip-flops 214, the LSI tester 300 inputs a clock signal to the clockterminal 209 at a desired time based on the delay time and so on havingbeen measured in step S1104. A phase difference between the desired timeand the timing of the rising edge or the falling edge of the referencesignal is an AC timing characteristic value to be tested and correspondsto, for example, a setup time and a hold time.

As described above, when the output signals are transmitted from thelast stage flip-flops 214, the clock signal generated by the secondmeasuring unit 305 is inputted to the clock terminal 209, so that theoutput signals transmitted from the output buffers 208 of the secondinput/output terminals 205 to be tested are latched by the flip-flops129 at the rising edge or the falling edge of the clock signal inputtedto the clock pins of the flip-flops 129 of the flip-flop circuits 121with the selectors (step S1107).

Next, the LSI tester 300 causes the flip-flop circuits 121 with theselectors to perform a shifting operation (step S1108). In other words,the LSI tester 300 operates the selectors 130 such that the first inputpins of the flip-flops 129 of the flip-flop circuits 121 with theselectors are connected to the third input pins of the selectors 130.Thereafter, the LSI tester 300 generates a clock signal in the secondmeasuring unit 305 and serially transmits the output signals having beenlatched by the flip-flop circuits 121 with the selectors, to the firstinput/output terminal 203.

The output signals having been inputted to the first input/outputterminal 203 are serially transmitted to a first measuring unit 302 ofthe LSI tester 300. The LSI tester 300 observes the transmitted outputsignals in the first measuring unit 302. Then, the LSI tester 300compares the logical values of the observed output signals with anexpected value and measures the delay times and so on of the outputsignals relative to the reference signal based on the comparison result.The expected value is the logical value of a test signal.

As described above, in a test on the AC characteristics of the outputsignals according to the third embodiment, the output signalssimultaneously supplied from the multiple terminals to be tested to theoutside of the semiconductor device can be serially transmitted from thesingle input/output terminal to the LSI tester, so that a large numberof terminals can be simultaneously tested using a small number ofterminals.

As in the second and third modifications of the semiconductor testingcircuit according to the first embodiment, a resistor connected to theend of the signal line 126 may be provided outside the semiconductordevice 200 and a switch circuit (sixth switch circuit) may be providedfor controlling electrical connection/disconnection between the firstinput/output terminal 203 not to be tested and the signal line 125 (theoutput pin of the flip-flop 129 of the last stage flip-flop circuit 121with the selector).

In the third embodiment, the terminals to be tested are input/outputterminals. An output terminal can be similarly tested.

Further, in the third embodiment, the output signal of the semiconductordevice is a logical signal, that is, the semiconductor device is a logicLSI and the like. As a matter of course, the present invention can besimilarly implemented even when the output signal is a pulse signalother than a logical signal.

1. A semiconductor testing circuit for testing AC characteristics of asemiconductor device, comprising: a first signal line connected to aterminal not to be tested and a plurality of terminals to be tested ofthe semiconductor device; first switch circuits for controllingelectrical connection/disconnection between the terminals to be testedand the first signal line; a first resistor connected to one end of thefirst signal line; and a second switch circuit for controllingelectrical connection/disconnection between the first signal line andthe terminal not to be tested, wherein at least the first signal lineand the first switch circuits are formed on the semiconductor device. 2.A semiconductor testing circuit for testing AC characteristics of asemiconductor device, comprising: a first signal line connected to aterminal not to be tested and a plurality of terminals to be tested ofthe semiconductor device; first switch circuits for controllingelectrical connection/disconnection between the terminals to be testedand the first signal line; a first resistor connected to one end of thefirst signal line; and input condition setting circuits respectivelybetween the terminals to be tested and the first signal line, the inputcondition setting circuit being capable of changing one of a logicalvalue and a delay amount of a signal inputted from the first signal lineto the terminal to be tested through the first switch circuit, whereinat least the first signal line and the first switch circuits are formedon the semiconductor device.
 3. The semiconductor testing circuitaccording to claim 2, wherein the first switch circuit is changed amonga state in which the first signal line and the terminal to be tested areelectrically connected to each other via the input condition settingcircuit, a state in which the first signal line and the terminal to betested are electrically connected to each other not via the inputcondition setting circuit, and a state in which the first signal lineand the terminal to be tested are electrically disconnected from eachother.
 4. A semiconductor testing method using the semiconductor testingcircuit according to claim 2, for testing AC characteristics of an inputsignal to terminals to be tested of a semiconductor device, the methodcomprising: operating the first switch circuits to electrically connectthe terminals to be tested and the first signal line, and setting one ofthe logical value and the delay amount of the signal from each of theinput condition setting circuits; inputting a test signal to the firstsignal line through the terminal not to be tested of the semiconductordevice, supplying to the semiconductor device a clock signal having adesired phase difference from the test signal, and causing first stageflip-flops provided in an internal circuit of the semiconductor deviceto respectively latch signals from the terminals to be tested; andcomparing the signals latched by the first stage flip-flops with anexpected value.
 5. A semiconductor testing circuit used for testing ACcharacteristics of a semiconductor device, comprising: a first signalline connected to a reference terminal of the semiconductor device, thereference terminal supplying, to outside of the semiconductor device, aclock signal having passed through an internal clock tree of thesemiconductor device; flip-flop circuits with selectors each of whichincludes a flip-flop having at least an output pin, a clock pin, and afirst input pin, and a selector having second and third input pins andelectrically connecting the first input pin and one of the second andthird input pins, the second input pins being respectively connected toterminals to be tested of the semiconductor device, the clock pins beingconnected to the first signal line; first switch circuits forcontrolling electrical connection/disconnection between the second inputpins of the flip-flop circuits with the selectors and the terminals tobe tested; second signal lines each of which connects the third inputpin of a flip-flop circuit with the selectors to the output pin of anadjacent flip-flop circuit with the selector, and connects the outputpin of the flip-flop circuit with the selector to a terminal not to betested of the semiconductor device when the output pin is not connectedto the third input pin; a second switch circuit for controllingelectrical connection/disconnection between the first signal line andthe reference terminal; and a first resistor connected to one end of thefirst signal line, wherein at least the first signal line, the flip-flopcircuits with the selectors, the first switch circuits, the secondsignal lines, and the second switch circuit are formed on thesemiconductor device.
 6. The semiconductor testing circuit according toclaim 5, wherein the first resistor is outside the semiconductor device.7. The semiconductor testing circuit according to claim 5, furthercomprising a third switch circuit for controlling electricalconnection/disconnection between the terminal not to be tested and theoutput pin of the flip-flop circuit with the selector.
 8. Asemiconductor testing method using the semiconductor testing circuitaccording to claim 5, for testing AC characteristics of an output signalsupplied from terminals to be tested of a semiconductor device tooutside of the semiconductor device, the method comprising: measuring adelay amount of the clock signal supplied from the reference terminal ofthe semiconductor device to outside of the semiconductor device throughthe internal clock tree of the semiconductor device, the referenceterminal being connected to the first signal line; operating the firstswitch circuits to electrically connect the terminals to be tested andthe second input pins of the flip-flop circuits with the selectors,operating the second switch circuit to electrically connect the firstsignal line and the reference terminal, and operating the selectors ofthe flip-flop circuits with the selectors to electrically connect thefirst input pins and the second input pins of the flip-flop circuitswith the selectors; supplying a clock signal to the semiconductor deviceto operate an internal circuit of the semiconductor device, inputting aclock signal to the reference terminal at a desired time based on themeasured delay amount when signals are supplied from last stageflip-flops in the internal circuit to the terminals to be tested, andcausing the flip-flops of the flip-flop circuits with the selectors tolatch the signals supplied from the terminals to be tested to theoutside of the semiconductor device; operating the selectors of theflip-flop circuits with the selectors to electrically connect the firstinput pins and the third input pins of the flip-flop circuits with theselectors, and serially transmitting, to the terminal not to be testedof the semiconductor device, the signals latched by the flip-flopcircuits with the selectors; and comparing the signals seriallytransmitted to the terminal not to be tested with an expected value.